This invention relates to novel antibacterial formulations, in particular to formulations including 6-(substituted-methylene) penems and derivatives thereof having xcex2-lactamase inhibitory and antibacterial properties. The invention also relates to methods for the preparation of such formulations and to uses thereof.
The compound ceftazidime, [6R -[6xcex1,7xcex2(Z)]]-1-[[7-[[(2-amino-4-thiazolyl)[(1-carboxy-1-methylethoxy)imino]acetyl]amino]-2-carboxy-8-oxo-5-thia-1-azabicyclo[4.2.0]oct-2-en-3-yl]methyl]pyridinium hydroxide inner salt, is a known and much used cephalosporin antibiotic compound. Ceftazidime is normally administered by injection as its pentahydrate. The term xe2x80x9cceftazidimexe2x80x9d as used herein includes all forms of ceftazidime including the free acid, hydrates, salts and ester thereof. Ceftazidime is susceptible to hydrolysis by xcex2xcex2-lactamase enzymes, for example those of B.fragilis, S. aureus and enterobactenaceae producing extended spectrum xcex2xcex2-lactamases or elevated levels of Class 1 enzymes.
The compound cefotaxime, [6R-[6xcex1,7xcex2(Z)]]-3-[(acetyloxy)methyl]-7-[[(2-amino-4-thiazoly)(syn-methoxyimoin)acetyl]amino-8-oxo-5-thia-1-azabicyclo[4.2.0]oct-2-ene-2-carboxylic acid, is a known and much used cephalosporin antibiotic compound. Cefotaxime is normally administered by injection as its sodium salt. The term xe2x80x9ccefotaaimexe2x80x9d as used herein includes all forms of cefotaxime including the free acid, salts and ester thereof. Cefotaxime is susceptible to hydrolysis by xcex2xcex2-lactamase enzymes, for example those of B.fragilis, Group 1 enzymes (typically encountered in Enterobacter Citrobacter and Pseudomonas), or showing mutational changes around the active site of the Group 2 enzymes TEM-1 and SHV-1 (typically encountered in E. coli and Klebsiella.
The compound amoxycillin, 6-[D(xe2x88x92)-xcex1-amino-p-hydroxypheny-acetamido]penicillanic acid, is a known and much used antibiotic compound. Amoxycillin is normally administered orally in the form of amoxycillin trihydrate, or parenterally as sodium amoxycillin. The term xe2x80x9camoxycillinxe2x80x9d as used herein includes all forms of amoxycillin including the free acid, salts and ester thereof. Amoxycillin is hydrolysed by a broad range of xcex2xcex2-lactamase enzymes, and is generally ineffective against organisms producing Group I and Group II xcex2xcex2-lactamases. Therefore amoxycillin is often administered together with a xcex2xcex2-lactamase inhibitor, for example clavulanic acid.
The compound piperacillin, 6-[[[[94-ethyl-2,3-dioxo-1-piperazinyl) carbonyl]amino]phenylacetyl]amino]-3,3-dimethyl-7-oxo-4-thia-azabicyclo [3.2.0]heptane-2-carboxylic acid, is a known and much used antibiotic compound. Piperacillin is normally administered parenterally as its sodium salt. The term xe2x80x9cpiperacillinxe2x80x9d as used herein includes all forms of piperacillin including the free acid, salts and ester thereof. Piperacillin is hydrolysed by xcex2xcex2-lactamase enzymes.
It is an object of this invention to provide novel combinations of xcex2xcex2-lactam antibiotics with a xcex2xcex2-lactamase inhibitor, having improved characteristics compared with known combinations.
According to the present invention, a pharmaceutical formulation comprises, in combination with a penem of formula (I): 
in which:
R1 is hydrogen or an organic substituent group;
R2 is a fused bicyclic heterocyclic ring system of general formula: 
xe2x80x83wherein R4 and R5 are independently hydrogen or one or more substituents replacing hydrogen atoms in the ring system shown; m is 2 or 3; p is zero, 1 or 2; and R3 is hydrogen, a salt-forming cation or an ester-forming group; and the symbol xe2x95x90/xe2x95x90 indicates that the double bond may be in either the E or Z configuration; and a pharmaceutically acceptable carrier; a xcex2xcex2-lactam antibiotic selected from the group consisting of cefotaxime, amoxycillin, piperacillin and ceftazidime, and their pharmaceutically acceptable derivatives including salts and in vivo hydrolysable esters.
Compounds of formula (I) are disclosed in WO94/10178 the contents of which are incorporated herein by way of reference.
The compound of formula (I), its salts and esters, may exist in a number of isomeric forms, all of which, including racemic and diastereoisomeric forms are encompassed within the scope of the formulations of the present invention.
Moreover, the compounds of formula (I) may exist in two isomeric forms at the methylene group at the 8-position, ie the E- and Z-isomeric forms. The Z-isomer is generally preferred as generally being the more active form.
Consequently preferred forms of the compounds of the present invention have the structure (IA): 
n general formula (1), R1 denotes hydrogen or an organic group, which may suitably be linked through a sulphur or carbon atom. For example, R1 may represent hydrogen or a group of formula xe2x80x94R5 or xe2x80x94SR5, where R5 denotes an unsubstituted or substituted (C1-10)hydrocarbon or heterocyclyl group.
Preferably, R1 represents hydrogen, (C1-10)alkyl or (C1-10)alkylthio, or substituted (C1-10)alkyl or substituted (C1-10)-alkylthio, wherein the substituent may be hydroxy, (C1-6)alkoxy, (C1-6)alkanoyloxy, halogen, mercapto, (C1-6)alkylthio, heterocyclylthio, amino, (mono or di)-(C1-6)alkylamino, (C1-6)alkanoylamino, carboxy, or (C1-6)alkoxycarbonyl.
Examples of suitable organic groups R1 include methyl, ethyl, propyl, methylthio, ethylthio, methylsulphinyl, ethylsulphinyl, hydroxymethyl, methoxymethyl, ethoxymethyl, acetoxymethyl, (1 or 2)-acetoxyethyl, aminomethyl, 2-aminoethyl, acetamidomethyl, 2-acetamidoethyl, carboxymethyl, 2-hydroxyethylthio, methoxymethylthio, 2-methoxyethylthio, acetoxymethylthio, 2-aminoethylthio, acetamidomethylthio, 2-acetamidoethylthio, carboxymethylthio, 2-carboxyethylthio, aryl(especially phenyl), arylthio (especially phenylthio), pyridyl, pyrimidyl, isoxazolyl, pyrimidylthio, tetrazolylthio, and pyridylthio groups.
In particular, R1 may be hydrogen.
Suitable groups R2 include: 2,3-dihydroimidazo[2,1-b]thiazol-6-yl, 2,3-dihydro-1-(R,S)-oxoimidazo[2,1-b)thiazol-6-yl, 2,3-dihydro-1,1-dioxoimidazo[2,1-b]thiazol-6-yl, 6,7-dihydro-5H-imidazo[2,1-b]-thiazin-2-yl and 6,7-dihydro-8,8-dioxo-5H-imidazo[2,1-b][1,3]thiazin-2-yl.
Examples of suitable substituents R4 and R5 include(C1-6)alkanoyl, (C1-6)alkanoyloxy, heterocyclyl, amino, (C1-6)alkanoylamino, (mono or di)-(C1-6)alkylamino, hydroxy, (C1-6)alkoxy, sulpho, mercapto, (C1-6)alkylthio, (C1-6)alkylsulphinyl, (C1-6)alkyl-sulphonyl, heterocyclylthio, arylthio, sulphamoyl, carbamoyl, amidino, guanidino, nitro, halogen, carboxy, carboxy salts, carboxy esters, arylcarbonyl, and heterocyclylcarbonyl groups, and also unsubstituted or substituted (C1-6)alkyl, (C2-6)alkenyl, (C2-6)alkynyl, aryl, and aryl(C1-6)alkyl groups.
Examples of suitable optional substituents for the above-mentioned (C1-6)alkyl, (C2-6)alkenyl, (C2-6)alkynyl, aryl and aryl(C1-6)alkyl substitutents include (C1-6)alkanoyl, (C1-6)alkanoyloxy, heterocyclyl, amino, (C1-6)alkanoylamino, (mono or di)-(C1-6)alkylamino, hydroxy, (C1-6)alkylsulphinyl, (C1-6)alkylsulphonyl, heterocyclylthio, arylthio, sulphamoyl, carbamoyl, amidino, guanidino, nitro, halogen, carboxy, carboxy salts, carboxy esters,arylcarbonyl and heterocyclylcarbonyl groups.
Suitably R4 and R5 may both be hydrogen.
Suitable pharmaceutically acceptable salts of the 3-carboxylic acid group of the xcex2xcex2-lactam antibiotic or the compound of formula (I) or of other carboxylic acid groups which may be present as optional substituents include those in which R3 is a metal ion e.g. aluminium salts, alkali metal salts (e.g. sodium, lithium or potassium salts), alkaline earth metal salts (e.g. calcium or magnesium salts), ammonium salts, and substituted ammonium salts, for example those with lower alkylamines (e.g. triethylamine), hydroxy-lower alkylamines (e.g. 2-hydroxyethylamine), di(2-hydroxyethyl)amine tri(2-hydroxyethyl)amine), bis-(2-hydroxy ethyl)amine, tris-(2-hydroxyethyl)amine, lower-alkylamines (e.g. dicyclohexylamine), or with procaine, dibenzylamine, N,N-dibenzyl- ethylenediamine, 1-ephenamine, N-methylmorpholine, N-ethylpiperidine, N-benzyl-b-phenethylamine, dehydroabietylamine, ethylenediamine, N,Nxe2x80x2-bishydroabietylethylenediamine, bases of the pyridine type (e.g. pyridine, collidine and quinoline), and other amines which have been or can be used to form quaternary ammonium salts with penicillins.
Pharmaceutically acceptable salts may also be acid addition salts of any amino or substituted amino group(s) that may be present as optional substituents on the compound of formula (I), or of any heterocyclic group ring nitrogen atoms. Suitable salts include for example hydrochlorides, sulphates, hydrogen sulphates, acetates, phosphates etc. and other pharmaceutically acceptable salts will be apparent to those skilled in the art. Suitable addition salts are the hydrochlorides and hydrogen sulphates. Preferred salts are sodium salts.
When R3 is an ester-forming group it may be a carboxylate protecting group or a pharmaceutically acceptable in-vivo hydrolysable ester.
Suitable ester-forming carboxyl-protecting groups are those which may be removed under conventional conditions. Such groups for R3 include benzyl, p-methoxybenzyl, benzoylmethyl, p-nitrobenzyl, 4-pyridylmethyl, 2,2,2-trichloroethyl, 2,2,2-tribromoethyl, t-butyl, t-amyl, allyl, diphenylmethyl, triphenylmethyl, adamantyl, 2-benzyloxyphenyl, 4-methylthiophenyl, tetrahydrofur-2-yl, tetrahydropyran-2-yl, pentachlorophenyl, acetonyl, p-toluenesulphonylethyl, methoxymethyl, a silyl, stannyl or phosphorus- containing group, an oxime radical of formula xe2x80x94Nxe2x95x90CHR6 where R6 is aryl or heterocyclyl, or an in vivo hydrolysable ester radical such as defined below.
A carboxyl group may be regenerated from any of the above esters by usual methods appropriate to the particular R3 group, for example, acid- and base-catalysed hydrolysis, or by enzymically-catalysed hydrolysis, or by hydrogenolysis under conditions wherein the remainder of the molecule is substantially unaffected.
Examples of suitable pharmaceutically acceptable in vivo hydrolysable ester groups include those which break down readily in the human body to leave the parent acid or its salt. Suitable ester groups of this type include those of part formulae (i), (ii), (iii), (iv) and (v): 
wherein Ra is hydrogen, (C1-6) alkyl, (C3-7) cycloalkyl, methyl, or phenyl, Rb is (C1-6) alkyl, (C1-6) alkoxy, phenyl, benzyl, (C3-7) cycloalkyl, (C3-7) cycloalkyloxy, (C1-6) alkyl (C3-7) cycloalkyl, 1-amino (C1-6) alkyl, or 1-(C1-6 alkyl)amino (C1-6) alkyl; or Ra and Rb together form a 1,2-phenylene group optionally substituted by one or two methoxy groups; Rc represents (C1-6) alkylene optionally substituted with a methyl or ethyl group and Rd and Re independently represent (C1-6) alkyl; Rf represents (C1-6) alkyl; Rg represents hydrogen or phenyl optionally substituted by up to three groups selected from halogen, (C1-6) alkyl, or (C1-6) alkoxy; Q is oxygen or NH; Rh is hydrogen or (C1-6) alkyl; Ri is hydrogen, (C1-6) alkyl optionally substituted by halogen, (C2-6) alkenyl, (C1-6) alkoxycarbonyl, aryl or heteroaryl; or Rh and Ri together form (C1-6) alkylene; Rj represents hydrogen, (C1-6) alkyl or (C1-6) alkoxycarbonyl; and Rk represents (C1-8) alkyl, (C1-8) alkoxy, (C1-6) alkoxy(C1-6)alkoxy or aryl.
Examples of suitable in vivo hydrolysable ester groups include, for example, acyloxyalkyl groups such as acetoxymethyl, pivaloyloxymethyl, xcex1-acetoxyethyl, a-pivaloyloxyethyl, 1-(cyclohexylcarbonyloxy)prop-1-yl, and (1-aminoethyl) carbonyloxymethyl; alkoxycarbonyloxyalkyl groups, such as ethoxy carbonyloxymethyl, xcex1-ethoxycarbonyloxyethyl and propoxycarbonyloxyethyl; dialkylaminoalkyl especially di-lower alkylamino alkyl groups such as dimethyl aminomethyl, dimethyl aminoethyl, diethylaminomethyl or diethylaminoethyl; 2-(alkoxy carbonyl)-2-alkenyl groups such as 2-(isobutoxycarbonyl)pent-2-enyl and 2-(ethoxycarbonyl)but-2-enyl; lactone groups such as phthalidyl and dimethoxy phthalidyl; and esters linked to a (second) xcex2xcex2-lactam antibiotic or xcex2xcex2-lactamase inhibitor.
A further suitable pharmaceutically acceptable in vivo hydrolysable ester group is that of the formula: 
wherein Rk is hydrogen, (C1-6 alkyl or phenyl.
When used herein the term xe2x80x98arylxe2x80x99 includes phenyl and naphthyl, each optionally substituted with up to five, preferably up to three, groups selected from halogen, mercapto, (C1-6) alkyl, phenyl, (C1-6) alkoxy, hydroxy(C1-6)alkyl, mercapto(C1-6)alkyl, halo(C1-6) alkyl, hydroxy, amino, nitro, carboxy, (C1-6) alkylcarbonyloxy, alkoxycarbonyl, formyl, or (C1-6) alkylcarbonyl groups.
The terms xe2x80x98heterocyclylxe2x80x99 and xe2x80x98heterocyclicxe2x80x99 as used herein include aromatic and non-aromatic, single and fused, rings suitably containing up to four hetero-atoms in each ring selected from oxygen, nitrogen and sulphur, which rings may be unsubstituted or substituted by, for example, up to three groups selected from halogen, (C1-6)alkyl, (C1-6)alkoxy, halo(C1-6)alkyl, hydroxy, carboxy, carboxy salts, carboxy esters such as (C1-6)alkoxycarbonyl, (C1-6)alkoxycarbonyl(C1-6)alkyl, aryl, and oxo groups. Each heterocyclic ring suitably has from 4 to 7, preferably 5 or 6, ring atoms. The term xe2x80x98heteroarylxe2x80x99 refers to heteroaromatic heterocyclic ring or ring system, suitably having 5 or 6 ring atoms in each ring. A fused heterocyclic ring system may include carbocyclic rings and need include only one heterocyclic ring. Compounds within the invention containing a heterocyclyl group may occur in two or more tautometric forms depending on the nature of the heterocyclyl group; all such tautomeric forms are included within the scope of the invention.
When used herein the terms xe2x80x98alkylxe2x80x99, xe2x80x98alkenylxe2x80x99, xe2x80x98alkynylxe2x80x99 and xe2x80x98alkoxyxe2x80x99 include straight and branched chain groups containing from 1 to 6 carbon atoms, such as methyl, ethyl, propyl and butyl. A particular alkyl group is methyl.
When used herein the term xe2x80x98halogenxe2x80x99 refers to fluorine, chlorine, bromine and iodine.
It will be appreciated that also included within the scope of the invention are formulations which utilise salts and carboxy-protected derivatives, including in vivo hydrolysable esters, of any carboxy groups that may be present as optional substituents in compounds of formula (I).
Certain compounds of formula (I) may include an amino group which may be protected. Suitable amino protecting groups are those well known in the art which may be removed under conventional conditions if required without disruption of the remainder of the molecule.
Examples of amino protecting groups include (C1-6) alkanoyl; benzoyl; benzyl optionally substituted in the phenyl ring by one or two substituents selected from (C1-4) alkyl, (C1-4) alkoxy, trifluoromethyl, halogen, or nitro; (C1-4) alkoxycarbonyl; benzyloxycarbonyl or trityl substituted as for benzyl above; allyloxycarbonyl,trichloroethoxycarbonyl or chloroacetyl.
Some compounds of formula (I) and (IA) may be crystallised or recrystallised from solvents such as organic solvents. In such cases solvates may be formed. This invention includes within its scope stoichiometric solvates including hydrates as well as compounds containing variable amounts of solvents such as water that may be produced by processes such as lyophilisation. Compounds of formula (I) and (IA) may be prepared in crystalline form by for example dissolution of the compound in water, preferably in the minimum quantity thereof, followed by admixing of this aqueous solution with a water miscible organic solvent such as a lower aliphatic ketone such as a di-(C1-6) alkyl ketone, or a (C1-6) alcohol, such as acetone or ethanol.
The compounds of formula (I) and (IA) are xcex2xcex2-lactamase inhibitors and/or antibiotics and are intended for use in pharmaceutical compositions. Therefore it will readily be understood that they are preferably each provided in substantially pure form, for example at least 60% pure, more suitably at least 75% pure and preferably at least 85% pure, especially at least 95% pure particularly at least 98% pure (% are on a weight for weight basis). Impure preparations of the compounds may be used for preparing the more pure forms used in the pharmaceutical compositions; these less pure preparations of the compounds should contain at least 1%, more suitably at least 5% and preferably from 10 to 59% of a compound of the formula (I) or (IA) or ester or salt thereof.
Compounds of formula (I), and in particular of formula (IA) are believed to be active xcex2xcex2-lactamase inhibitors, and to have the further advantage of improved pharmacokinetics.
Accordingly, specific compounds of formula (I) include the following pharmaceutically acceptable salts:
Sodium (5R)-6-[(Z)-(2,3-dihydroimidazo[2,1-b]thiazol-6-yl) methylene]-penem-3-carboxylate.
Sodium (5R)-6-[(Z)-(2,3-dihydro-1(R,S)-oxoimidazo[2,1-b]thiazol-6yl)methylene]penem-3-carboxylate.
Sodium (5R)-6-[(Z)-(2,3-dihydro-1,1-dioxoimidazo[2,1-b]thiazol-6yl)methylene]penem-3-carboxylate.
Sodium (5R)-6-[(Z)-(6,7-dihydro-5H-imidazo[2,1-b][1,3]thiazin-2yl)methylene]penem-3-carboxylate.
Sodium (5R)-6-[(Z)-(6,7-dihydro-8,8-dioxo-5H-imidazo[2,1-b][1,3]thiazin-2-yl)methylene]penem-3-carboxylate.
Compounds of formula (I) as defined above may be prepared by subjecting a compound of the formula (II): 
wherein R1 and R2 are as defined in formula (I) above, Rx is a carboxyprotecting group, X is a halogen atom, and Z denotes a halogen atom, a hydroxy group, a substituted hydroxy group, an xe2x80x94S(O)qR7 group or an xe2x80x94Se(O)rR7 group where q denotes 0,1 or 2, r denotes 0 or 1, and R7 denotes a hydrogen atom, a hydrocarbon group or a heterocyclyl group, to a reductive elimination reaction to eliminate the elements of the group X and Z,
and thereafter if necessary or desired:
(i) converting the group Rx to a different group Rx such as a substituent R3,
(ii) converting the group R2 into a different group R2,
(iii) converting the group OR5 into a different group OR5.
(iv) converting the compound into a pharmaceutically acceptable salt.
The reductive elimination reaction may be carried out in a manner known per se for such elimination reactions for example as described in EP 0232966A. The elimination may for example be carried out by reaction with a metal, for example zinc, magnesium, aluminium, or iron, in the presence of an acid (for example, acetic acid or a mineral acid), or by reaction with a triorganophosphorus compound, for example triphenylphosphine, suitably at a temperature within the range of from xe2x88x9220xc2x0 C. to +40xc2x0 C., preferably from 0xc2x0 C. to 20xc2x0 C. The reaction may be carried out in the presence of a polar or non-polar, protic or aprotic, organic solvent, for example dioxane, dimethoxyethane, or tetrahydrofuran.
The product of this reaction is generally a mixture of isomers of the E and Z isomers of formula (I). The desired isomer of the general formula (I) may be isolated and purified in conventional manner for example by known crystallisation or chromatographic techniques. Moreover, the carboxy group xe2x80x94COORx may be deprotected, that is to say, converted to a free carboxy, carboxy salt or carboxy ester group xe2x80x94COOR3 in a conventional manner, for example as described in EP0232966A.
When it is desired to obtain a free acid or salt of the preferred penem isomer of the formula (I) from such an isomeric mixture, this may be effected by chromatographic separation of the product followed by deprotection of the desired isomer to give the corresponding free acid or salt. In some cases, however, it has been found particularly convenient first to deprotect the isomeric mixture to give an isomeric mixture of the free acid or salt of formula (I), followed by fractional recrystallisation to give the desired acid or salt isomer.
Compounds of formula (II) in which Z is a hydroxy group may be prepared by the reaction of known (see EP0232966) compounds of formula (III): 
where X, R1 and Rx are as defined in formula (II), with an aldehyde of formula (IV):
R2xe2x80x94CHOxe2x80x83xe2x80x83(IV)
where R2 is as defined in formula (II), thereby forming the corresponding halohydrin of formula (II).
The reaction between the compound (III) and the aldehyde (IV) may suitably be carried out in the presence of a base, preferably a non-nucleophilic base, and preferably a strong base. Suitable bases include, for example, lithium amide bases, for example lithium bistrimethyl silylamide, lithium dicyclohexlamide, lithium diisopropylamide, lithium 2,2,6,6-tetramethylpiperidide, lithium diphenylamide, and butyllithium.
Suitable solvents for the reaction are aprotic organic solvents (which may be polar or non-polar), for example tetrahydrofuran, toluene, dimethoxyethane, dimethylformamide, and mixtures of two or more such solvents.
The reaction may suitably be carried out at a temperature within the range of from xe2x88x92100xc2x0 C. to ambient temperature, preferably from xe2x88x9285xc2x0 C. to 0xc2x0 C., especially from xe2x88x9285xc2x0 C. to 40xc2x0 C.
The aldehyde of the general formula (IV) and the base may be added to the halo-penem (III) in either order. If it is desired to isolate the halohydrin-penem of the general formula (II) in which Z denotes a hydroxy group, the reaction mixture may conveniently be quenched by adding a protic reagent, for example an acid, such as acetic acid or citric acid, or water.
Aldehydes of formula (IV) may be prepared from known (e.g. Reuben G Jones, CA: (45) 7153e, U.S. Pat. No. 2,541,924) compounds of formula (V): 
where R is alkyl, e.g. (C1-6) alkyl, and R5 is as defined above, by reaction with known compounds of formula (VI): 
where m is as defined above, and X and Y are halogen, preferably chlorine or bromine. Preferably one of X or Y is chlorine and the other is bromine. A compound of formula (VII) is formed: 
The reaction between compounds (V) and (VI) may be carried out in an organic solvent e.g. DMF, in the presence of a base, such as triethylamine.
I The compound (VII) may be cyclised, for example by treatment with an alkali metal hydride such as sodium hydride in a solvent such as THF, to form a compound (VIII): 
Compounds of formula (VIII) may then be converted to compounds of formula (IV) by various procedures.
For example the CO2R group of the compound (VIII) may be reduced, using for example di-isobutylaluminium hydride to form the corresponding aldehyde (IV) having p as zero. The corresponding aldehyde (IV) having p as 1 or 2 may then be prepared by oxidation of the S atom using a peroxy acid such as chloroperbenzoic acid.
Alternatively for example the compound (VIII) may be treated with a peroxy acid, e.g. as above, to oxidise the S atom and form the sulphoxide or sulphone analogue of compound (VI), followed by reduction of the CO2R group to an aldehyde group e.g. as above to form an aldehyde (IV) having p as 1 or 2.
Alternatively for example the CO2R group of compound (VIII) may be partly reduced to form the corresponding hydroxymethyl compound (IX): 
for example using lithium aluminium hydride. The hydroxymethyl compound (IX) may then for example be further oxidised, e.g. using Mn(IV), e.g. MnO2, to form the corresponding aldehyde (IV) having p as zero, and which may then be further oxidised using a peroxy acid to form an aldehyde (IV) having p as 1 or 2.
Alternatively the hydroxymethyl compound (IX) may be oxidised using a peroxy acid, e.g. as above to form the corresponding sulphoxide or sulphone (IX), and this sulphoxide or sulphone may then be further oxidised, e.g. using Mn (IV) as above to convert the hydroxymethyl group of (IX) to an aldehyde group, to form an aldehyde (IV) having p as 1 or 2.
Alternatively for example the hydroxymethyl compound (IX) may be acylated to form a compound (X): 
were A is an acyl group, for example a (C1-6) acyl group such as acetyl. Acylation may be by the use of an acylating derivative of A, for example an acyl halide or an acid anhydride. The compound (X) may then be oxidised using a peroxy acid to form the corresponding sulphoxide or sulphone. The hydroxymethyl group may then be regenerated, e.g. by treatment with methanolic ammonia, followed by oxidation of the hydroxymethyl group e.g. using Mn (IV) as above to form the corresponding aldehyde group in an aldehyde (IV).
Compounds of formula (II) in which Z is a substituted hydroxy group or a group of formula xe2x80x94S(O)qR7 or xe2x80x94Se(O)rR7 may be prepared from compounds of formula (II) in which Z is hydroxy by known methods, for example as described in EP 0232966A.
When Rx is a carboxylate protecting group, such as 4-methoxybenzyl, these protecting groups may be removed to form the parent acid by methods well known in the art, for example in the case of 4-methoxybenzyl treatment with a Lewis acid such as ethyl aluminium dichloride or aluminium chloride. Pharmaceutically acceptable salts may be prepared from such acids by treatment with a base, after a conventional work-up if necessary. Suitable bases include sodium hydrogen carbonate to form sodium salts.
Crystalline forms of the compounds of formula (1) may for example be prepared by dissolving the compound (I) in the minimum quantity of water, suitably at ambient temperature, then adding a water miscible organic solvent such as a (C1-6) alcohol or ketone such as ethanol or acetone, upon which crystalisation occurs and which may be encouraged for example by cooling or trituration.
The compounds of formula (I) have xcex2xcex2-lactamase inhibitory and antibacterial properties. Compounds of formula (I) provide xcex2xcex2-lactam antibiotics with protection against the xcex2xcex2-lactamase enzymes of such microorganisms as B.fragilis, S.aureus, and strains of Enterobacteniaceae producing extended spectrum xcex2xcex2-lactamases, strains producing high levels of Group 1 xcex2xcex2-lactamase, K.pneumoniae, and Ent. Cloacae. 
Compounds of formula (I) provide amoxycillin with protection against most of the medically important Group I and Group II xcex2xcex2-lactamase producing organisms at in vitro concentrations as low as 0.25 xcexcg/ml. Protection is also observed against problem xcex2xcex2-lactamase producing organisms such as high level xcex2xcex2-lactamase producing strains of Ent.Cloacae P99 and E. coli JT4 (Group IIb). Synergy between compounds of formula (1) and amoxycillin is also observed against B.fragilis, xcex2xcex2-lactamase producing S. aureus, and against most Gram negative producing Group II or inducible Group I xcex2xcex2-lactamases, and against organisms producing high levels of Group I xcex2xcex2-lactamase. Protection against the xcex2xcex2-lactamases produced by Pseudomonas aeruginosa is also observed.
The pharmaceutical formulations of the invention are useful for the treatment of infections in animals, especially mammals, including humans, in particular in humans and domesticated (including farm)animals. The formulations of this invention may be used, for example, for the treatment of infections for which a xcex2xcex2-lactam antibiotic is normally administered, for example of, inter alia, the respiratory tract, urinary tract, and soft tissues, especially in humans. The formulations of this invention may be used for the treatment of infections caused by strains of, for example, the organisms mentioned above.
Some compounds of formula (I), for example sodium (5R)-6-[(Z)-(2,3-dihydroimidazo[2,1-b]thiazol-6-yl)methylene]penem-3-carboxylate, appear to have an advantageously long serum half life. The compound of formula (I) or (IA) and the xcex2xcex2-lactam antibiotic can be administered separately or in the form of a single formulation containing both active ingredients as discussed in more detail below.
The compounds of formula (I) or (IA) may be formulated for administration in any convenient way for use in human or veterinary medicine, by analogy with other antibiotics. The compounds of formula (I), particularly (IA) are particularly suitable for parenteral administration.
The formulation may be formulated for administration by any route, such as oral, topical or parenteral. The compositions may be in the form of tablets, capsules, powders, granules, lozenges, creams or liquid preparations, such as oral or sterile parenteral solutions or suspensions.
The topical formulations of the present invention may be presented as, for instance, ointments, creams or lotions, eye ointments and eye or ear drops, impregnated dressings and aerosols, and may contain appropriate conventional additives such as preservatives, solvents to assist drug penetration and emollients in ointments and creams.
The formulations may also contain compatible conventional carriers, such as cream or ointment bases and ethanol or oleyl alcohol for lotions. Such carriers may be present as from about 1% up to about 98% of the formulation. More usually they will form up to about 80% of the formulation.
Tablets and capsules for oral administration may be in unit dose presentation form, and may contain conventional excipients such as binding agents, for example syrup, acacia, gelatin, sorbitol, tragacanth, or polyvinylpyrollidone; fillers, for example lactose, sugar, maize-starch, calcium phosphate, sorbitol or glycine; tabletting lubricants, for example magnesium stearate, talc, polyethylene glycol or silica; disintegrants, for example potato starch; or acceptable wetting agents such as sodium lauryl sulphate. The tablets may be coated according to methods well known in normal pharmaceutical practice. Oral liquid preparations may be in the form of, for example, aqueous or oily suspensions, solutions, emulsions, syrups or elixirs, or may be presented as a dry product for reconstitution with water or other suitable vehicle before use. Such liquid preparations may contain conventional additives, such as suspending agents, for example sorbitol, methyl cellulose, glucose syrup, gelatin, hydroxyethyl cellulose, carboxymethyl cellulose, aluminium stearate gel or hydrogenated edible fats, emulsifying agents, for example lecithin, sorbitan monooleate, or acacia; non-aqueous vehicles (which may include edible oils), for example almond oil, oily esters such as glycerine, propylene glycol, or ethyl alcohol; preservatives, for example methyl or propyl p-hydroxybenzoate or sorbic acid, and, if desired, conventional flavouring or colouring agents.
Suppositories will contain conventional suppository bases, e.g. cocoa-butter or other glyceride.
For parenteral administration, fluid unit dosage forms are prepared utilizing the compound of formula (I), xcex2xcex2-lactam and a sterile vehicle, water being preferred. These compounds, depending on the vehicle and concentration used, can be either suspended or dissolved in the vehicle. In preparing solutions these compounds can be dissolved in water for injection and filter sterilised before filling into a suitable vial or ampoule and sealing.
Advantageously, agents such as a local anaesthetic, preservative and buffering agents can be dissolved in the vehicle. To enhance the stability, the formulation can be frozen after filling into the vial and the water removed under vacuum. The dry lyophilized powder is then sealed in the vial and an accompanying vial of water for injection may be supplied to reconstitute the liquid prior to use. Parenteral suspensions are prepared in substantially the same manner except that the compound is suspended in the vehicle instead of being dissolved and sterilization cannot be accomplished by filtration. The compound can be sterilised by exposure to ethylene oxide before suspending in the sterile vehicle. Advantageously, a surfactant or wetting agent is included in the composition to facilitate uniform distribution of the compound.
The formulations may contain from 0.1% by weight, preferably from 10-60% by weight, of the active materials, depending on the method of administration. Where the formulations comprise dosage units, each unit will preferably contain from 50-500 mg of the active ingredient. The dosage as employed for adult human treatment will preferably range from 100 to 3000 mg per day, for instance 1500 mg per day depending on the route and frequency of administration. Such a dosage corresponds to 1.5 to 50 mg/kg per day. Suitably the dosage is from 5 to 20 mg/kg per day.
No toxicological effects are indicated when a formulation in accordance with the invention is administered in the above-mentioned dosage range.
A formulation according to the invention may comprise a single xcex2xcex2-lactam antibiotic and a compound of formula (I) or (IA) as the sole active ingredients or therapeutic agents, or it may also comprise one or more additional active ingredients or therapeutic agents, for example a second xcex2xcex2-lactam antibiotic, or pro-drug thereof.
Ceftazidime may be used in the form of the free acid, e.g as its pentahydrate.
Cefotaxime may be used in the form of the free acid or its pharmaceutically acceptable salts, for example its sodium salt.
Amoxycillin may be used in the form of amoxycillin trihydrate or its pharmaceutically acceptable salts, for example its sodium salts. Alternatively, amoxycillin may be used in the form of fine particles of its zwitterionic form (generally as amoxycillin trihydrate) for use in an injectable or infusable suspension, for example, in the manner hereinbefore described. Amoxycillin in the form of its sodium salt or the trihydrate is particularly preferred for use in synergistic compositions according to the invention.
Piperacillin may be used in the form of its pharmaceutically acceptable salts, for example its sodium salts, in an injectable or infusable suspension, for example, in the manner hereinbefore described. Piperacillin in the form of its sodium salt is particularly preferred for use in synergistic formulations according to the invention.
A compound of formula (I) or (IA) may be administered to the patient in a synergistically effective amount, together with xcex2xcex2-lactam antibiotic.
The compounds of formula (I) or (IA) may suitably be administered to the patient at a daily dosage of from 0.7 to 50 mg/kg of body weight. For an adult human (of approximately 70 kg body weight), from 50 to 3000 mg, preferably from 100 to 1000 mg, of a compound according to the invention may be adminstered daily, suitably in from 1 to 6, preferably from 2 to 4, separate doses. Higher or lower dosages may, however, be used in accordance with clinical practice.
When the compositions according to the invention are presented in unit dosage form, each unit dose may suitably comprise from 25 to 1000 mg, preferably from 50 to 500 mg, of a compound of formula (I). Each unit dose may, for example, be 62.5, 100, 125, 150, 200 or 250 mg of a compound of formula (I).
The ratio of the amount of the compound of formula (I) to the amount of xcex2-lactam antibiotic(s) may vary within a wide range. The said ratio may, for example, be from 100:1 to 1:100; more particularly, it may, for example, be from 2:1 to 1:30.
The amount of xcex2xcex2-lactam antibiotic administered in a formulation according to the invention, i.e in unit doses or the total amount per day will normally be approximately similar to the amount in which it is conventionally used pr se,.
The amount of cefotaxime in a formulation according to the invention will normally be approximately similar to the amount in which it is conventionally used per se, for example 1-2 g intraveneously or intraveneously every 8 hours, up to a maximum of 12 g daily.
The amount of amoxycillin in a formulation according to the invention will normally be for example from about 50 mg, advantageously from about 62.5 mg, to about 3000 mg per unit dose, more usually about 125, 250, 500, 625, 875 or 1000 mg per unit dose up to the normal maximum with or daily dose of amoxycillin.
The present invention provides a formulation as described above for use as a therapeutic agent.
The present invention further provides a formulation as described above for use in the treatment of bacterial infections.
The present invention includes a method of treating bacterial infections in humans and animals which comprises the administration of a therapeutically effective amount of a formulation as described above.
The present invention also includes the use of formulation as described above, in the manufacture of a medicament for the treatment of bacterial infections, either alone or in combination.